textproduct: Rapid City

KEY MESSAGES

- Passing showers with thunderstorm chances track into the area from the south tonight.

- A cold front tomorrow will swing winds to the northwest and drag cooler air into NE WY and W SD. Thunderstorm redevelopment is possible along the front but best chances are east of the CWA.

- Another round of rain, snow in Black Hills, is likely late Sunday into Monday.

- Much colder to start the week but warmer temps return by late week.

DISCUSSION

(This Evening Through Saturday) Issued at 149 PM MDT Sat May 16 2026

A weather pattern change has begun. Latest water vapor satellite imagery (20z) shows the deepening upper level low over the NW CONUS. This low is forecast to track eastward over the next couple of days, bringing active weather to the central states. The bulk of the impacts from this low will be felt farther south and east of the CWA but NE WY and W SD will see big changes in the weather from this low.

Through the day today, showers have developed along a boundary in northern Nebraska. These showers are moving northeast but so far, these have been just general showers with no lightning detected. For this evening and overnight, showers and thunderstorms will continue to develop to our southwest and track into the CWA. The severe weather tonight is expected to our south so general thunderstorms are in the forecast for W SD, NE WY has an even lesser chance of seeing thunder.

Tomorrow, Sunday, could play out to be an interesting weather day. It's looking like a surface low will develop near the NE-WY- to- Black-Hills area early Sunday morning and track eastward. As it does, it will develop a cold front that will swing to the south- side of the low. As the cold front slides east, thunderstorm development is possible. The timing of the cold front will highly influence where the strongest storms will be. A slower moving front will lead to more storms in western SD while a quicker moving front will lead to most of the thunderstorm action happening to the east of the CWA. For now, it's looking like a quicker moving front is the most likely scenario but uncertainty is still high at this time. Also, forecast CAPE values for tomorrow are pretty low in our area but with plenty of shear, any ongoing convection may end up continuing well into the morning before fading out.

Another impact from this passing cold front will be the gusty northwest winds behind the front. As the front pushes eastward, wind gusts upwards of 35 to 45 mph are likely. Elected to not issue a wind advisory for these gusty winds at this time because the window of those strongest winds is brief, mainly less than 2 hours. So once the front clears your area, you can expect the wind speeds to increase then steadily diminish through the afternoon.

For Monday, an upper level disturbance will quickly move through, keeping widespread passing precip chances in the area. Through Monday night, total QPF amounts are around around .25 to .65 inches, highest amounts in the SD plains.

As cooler air slides into the area behind the cold front, we are looking at a taste of winter-like weather. For starters, some of the precip will likely fall as snow in the higher elevations of the Black Hills. At this times, upwards of 2 to 6 inches of snow is possible. A big question is - will it accumulate or will it melt as it hits the ground? Either way, a slushy, wet snow is likely Sunday night into Monday.

Temperatures will also dip well below normal for mid-to-late May. Overnight lows will dip into the 20s to 30s Sunday night through Tuesday night. Monday's temps could very well stay steady or decrease through the day as the cooler air moves in. But the colder temps won't last long as highs in the 50s are likely Tuesday with a warming trend expected for the rest of the week.

AVIATION

(For the 00Z TAFS Through 00Z Sunday Evening) Issued At 512 PM MDT Sat May 16 2026

Generally VFR conditions are expected this evening. Isolated to scattered showers are expected to move in this evening, while some thunder is possible with these showers, have opted to leave mentions out of TAFs due to low confidence. VFR conditions likely in any showers, but cannot rule out some brief MVFR. MVFR/IFR cigs and widespread rain showers are expected to filter in after 17/10Z and will dissipate by 17/22Z.

FIRE WEATHER

Issued At 149 PM MDT Sat May 16 2026

Elevated fire weather conditions have been reported around the area today and will linger into the evening hours tonight.

Cooler with shower chances begin tonight through early next week, leading to a break in fire weather concerns although the best chance for wetting rains will be east of the area.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.